One in five (21% of) 14- to 15-year-olds report having been cyber bullied, up from 4% in eight- to nine-year-olds. Bullies post threatening messages, spread rumours and share humiliating images via sites such as Facebook, YouTube, Snapchat and Instagram for teenagers, and Moshi Monsters and Club Penguin for pre-teens.

But contrary to public perception, bullying via social media is not as common as traditional forms of face-to-face bullying.

It's natural for parents to want to protect their children and teens from bullying on social media, but simply taking their devices away is not the solution.

There is also a cumulative effect: the more experiences of bullying (whether cyber or tradtional), the worse the mental health risk.

Social media can be good and bad

Most Australian children (78%) have used social media by the ages of eight or nine. Usage increases during teenage years, with most 16-17 year olds (92%) accessing it at least once a month, and around half with daily access.

When parents see a problem, it's sometimes tempting to try to ban children from using social media. But a ban is difficult to enforce, given the reliance on the internet for education.

It may also be counter-productive. Most 14- to 17-year-olds report that the internet is very important to them, saying it improves their wellbeing and relationships.

A recent review of international research confirms that participation in social media can increase teenagers' feelings of self-esteem, support, and fitting in with a group. Children relate to each other through social media, for good and for bad.

Setting up safe processes

You can help your child from being targeted by adequately supervising them when they're online, only providing access to social media sites that are appropriate for their level of maturity, and maintaining good lines of communication.

To help decide whether social media sites are appropriate for your child's age, read the "terms of use" and check the minimum age. You can then help your child to set an appropriate privacy setting.

It's important to educate you child about about internet safety. This includes ensuring they only "friend" people they know in real life, and that they consider the possible impacts of information before posting.

Try keeping computers only in the common area of the house, friending or following your child online, and occasionally checking their online profile.

Over time, you can give your child more independence as they develop their skills to manage more complicated situations online. But try to maintain good communication so they can come to you with any problems - this includes listening without overreacting.

Look out for signs of distress, such as greater emotional reactivity, avoiding school or social situations, sleep disturbance, or a drop in school marks.

If your child is unwilling to speak with you, they may be willing to call a support service such as the Kids Helpline.

What if your child has a problem?

If the problem involves someone he or she knows in real life, your child might be able to sort out the problem directly. Or you can ask the school for help.

You can help your child decide whether to block or unfriend online users who are causing distress. It's wise to keep a record of problems, by taking screen shots. Offensive content can be reported to the website or carrier, and if not addressed, can be reported to the Children's eSafety Commissioner.

If you think your child is in danger, contact the police or Crimestoppers.

Finally, if your child suffers ongoing distress, consider getting professional help from a psychologist, psychiatrist or your GP.